The competition between different degrees of freedom in the structure of the quintet states of negative parity of some even-even Sn isotopes

Levels 2⁺, 3⁻, 1⁻, 2⁻, 3⁻¹, 5⁻ are interpreted as eigenvalues of a boson expanded Hamiltonian containing a shell model term, pairing, and quadrupole-quadrupole and octupole-octupole interaction. The expansion is performed in terms of standard RPA noncollective phonons and the so-called correlated phonons which are related to the RPA collective phonons by a canonical transformation whose parameters are determined so that the energy of the ground state is minimum. The noncollective degrees of freedom are included via an effective Hamiltonian depending on energy. Formalism is applied to ¹¹⁴Sn, ¹¹⁶Sn, and ¹¹⁸Sn. Also, transition probabilities and quadrupole moments are calculated. Results are compared with experimental data as well as with the previous theoretical calculations.     

Dose assessment of bremsstrahlung induced by beta-emitting radioisotopes of uranium-238 series and lead in human tissues

In the natural uranium-238 decay series, pure beta isotopes such as ²³⁴Th, ²³⁴Pa, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb and ²¹⁰Bi are released. The few lead isotopes such as ²¹¹Pb, ²¹²Pb, ²¹³Pb and ²¹⁵Pb are good beta emitters. In certain nuclear reactions of reactor these isotopes are released. These beta isotopes have maximum beta energies, which induce the bremsstrahlung radiation. The bremsstrahlung component of these beta isotopes has been traditionally ignored in dosimetry calculations. The shapes of bremsstrahlung spectra are a basic ingredient in the understanding and quantification of beta-ray dosimetry. The bremsstrahlung spectra produced by these high-energy isotopes such as ²³⁴Th, ²³⁴Pa, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb, ²¹⁰Bi, ²¹¹Pb, ²¹²Pb, ²¹³Pb and ²¹⁵Pb in bone, muscle and teeth are studied, and the computed spectral distributions are presented. The spectral shapes are primarily responsible for variations in the shapes of depth–dose distributions. They are intended to provide a quick and convenient reference for spectral shapes and to give an indication of the wide variation in these shapes. The evaluated beta bremsstrahlung dose as a function distance for the studied nuclides is also presented. The efficiency, intensity and dose rate of bremsstrahlung induced by beta isotopes of natural uranium-238 decay series and beta-emitting lead isotopes in human tissues such as brain, breast, heart, kidney, liver, muscle, pancreas and bone have also been studied in the present investigation. The values of bremsstrahlung dosimetric parameters are low for pancreas, but they are high for bone. For all studied tissues these parameters are high for ²³⁴Pa, but low for ²¹⁰Pb.     

Semiclassical analysis of α-transfer reactions

Semiclassical concepts are used to gain insight into α-transfer reactions. These reactions, interpreted as one-step direct reactions on the basis of DWBA analyses, are treated in analogy with single nucleon transfer reactions for which it is known that semiclassical methods are successful. In this case however the probability of transfer appears to be greatest at a distance of closest approach which is larger than the grazing distance by the order of the α-particle radius. This increase in the effective “grazing” distance is interpreted as a manifestation of the α-particle size at the time of transfer. Angular distributions are calculated semiclassically for the reactions ²⁰⁸Pb(¹⁶O, ¹²C)²¹²Po at 93 MeV and ⁴⁰Ca(¹²C, ⁸Be)⁴⁴Ti at 45 MeV lab energy. They are seen to give a reasonable fit to experiment. Partial wave amplitudes for transfer are also studied.     

Excited states of HCl

Ab initio CI calculations are presented for potential curves for the valence states of HCl, for the vertical electronic spectrum and for the potential curve for the B ¹Σ⁺ state. The valence ¹Π, ³Π and ³Σ⁺ states are found to be repulsive. Calculated vertical excitation energies are in good agreement with experiment. The B ¹Σ⁺ curve is predicted to have a double minimum.     

Effects of ground-state correlations on 2νββ decay rates and limitations of the QRPA approach

Half-lives of the 2νββ decay are calculated in the proton-neutron QRPA for⁷⁶Ge,⁸²Se,¹⁰⁰Mo,^128,130Te,¹³⁶Xe and¹⁵⁰Nd. The strength of the particle-particle interaction, which plays a decisive role for a reliable evaluation of the half-lives, is determined from a QRPA calculation of singleβ ⁺ decays. The 2ν decay rates calculated with the interaction strength fitted in this way are strongly suppressed and found to be consistent with the existing experimental data. Effects of the ground-state correlations on the suppression are investigated. On the other hand, the present calculation indicates limitations of the QRPA approach.     

Spin distributions in the vibrational excitations of closed-shell nuclei

Self-consistent Hartree-Fock and RPA calculations with the Skyrme-type interaction SGII are used for a systematic investigation of the 1⁺ and the triplet 0^?, 1^?, 2^? states in ⁴⁰Ca and ²⁰⁸Pb. Response functions to spin-dependent multipole operators are calculated and the particle-hole structure of the spin-dependent collective states is studied. Collective spin-dependent 0^? and 1^? states above the giant dipole resonance as well as a collective spin-independent 2^? state (twist mode) are identified. Transition spin and current densities are calculated for the collective excitations and found to be useful for the study of these excitation modes.     

Preparation of Naturally 13C-Rich Free Fatty Acids (FFA) from Corn Oil and their Application in Metabolic Studies of Lactating Cows

Abstract

When the ¹³C/¹²C ratios in lactose and milk fat of normally fed healthy cows are compared to ¹³C/¹²C in feed a metabolic depletion of ¹³C in the milk constituents becomes obvious.

Due to a carbon isotope effect in the decarboxylation step of pyruvate to Acetyl-Co-A resulting in a ¹³C depleted acetate, depot fat and milk fat are especially reduced in ¹³C relative to ¹²C.

Under pathophysiological conditions after longer fasting periods or in ketosis, long chain fatty acids from depot fat are metabolized and their ¹³C depleted carbon atoms enter the citric acid cycle via Acetyl-Co-A. Then the intermediary products of this cycle become ¹³C depleted too and with a drain on the oxalacetate pool by gluconeogenesis ¹³C depleted carbon atoms are channeled into lactose.

This hypothesis is apt to explain a ¹³C/¹²C decrease in lactose of ketotic cows relative to healthy controls. It is supported by the observation that ¹³C-rich fatty acids from corn oil dosed orally to a ketotic cow increase the ¹³C/¹²C ratios in lactose. So a crossing-over of carbon atoms from long chain fatty acids into glucose and lactose seems highly probable.     

Determination of Separated Plutonium,Americium and Curium in Environmental Samples by Sequential Extraction Techniques

A simple, reliable and practical radiochemical method for sequential isolation and determination of plutonium, americium and curium in a wide variety of environmental samples including soils, river sediments and water was developed. The isotopes determined are: ²³⁸Pu, ^239,240Pu, ²⁴¹Am, ²⁴²Cm and ²⁴⁴Cm. The methods involve leaching of soil or sedimental samples with concentrated nitric acid using a pressure digestion technique. Subsequent concentration and separation of nuclides of interest from major matrix elements and other interfering alpha-emitters are carried out by coprecipitation with ferric hydroxide and solvent extractions. Sources suitable for alpha-spectrometry are prepared by electrodeposition from acidic ammonium chloride solution. ²⁴²Pu and ²⁴³Am are used as tracer isotopes of plutonium and americium-curium elements, respectively. Some results of analysis of soils, sediments and water are given. The alpha peaks from ²³⁸Pu, ^239,240Pu and ²⁴²Pu as well as ²⁴¹Am, ²⁴⁴Cm, ²⁴²Cm and ²⁴³Am are well resolved. The entire analytical procedures for plutonium, americium and curium are completed in less than sixteen hours.     

Ab initio study of the feasibility of laser cooling of ScO molecule

ABSTRACT

Using ab initio quantum chemistry method, the feasibility of laser cooling ScO was investigated. The ground state Χ²Σ⁺ and low-lying excited states Α²Π, Α′²Δ are calculated at the multi-reference configuration interaction (MRCI) level of theory. The calculated spectroscopic constants are in good agreement with available theoretical and experimental results. At the MRCI level of theory with Davidson correction, the permanent dipole moments of the Χ²Σ⁺ and Α²Π states of ScO are also calculated. The highly diagonally distributed Franck–Condon factors and shorter radiative lifetime for the Α²Π→Χ²Σ⁺ transition are calculated with the corresponding potential energy curves and transition dipole moment. Although there is an intermediate state Α′²Δ, the loss will be dominated by branching to the intermediate electronic state Α′²Δ at a level of η < 1.4 × 10^?4. These results demonstrate the probability of laser cooling of ScO, and we provide a promising laser-cooling scheme for ScO molecule.     

Transfer reactions of B with Ta

Excitation functions and mean recoil ranges are reported for the formation of ¹⁸²Os, ¹⁸³Re, ¹⁸²Re, ¹⁸¹Re and ¹⁸²Ta in ^{10, 11}B interactions with ¹⁸¹Ta. The stacked foil technique was used. The results are indicative of formation through a transfer reaction. We have considered a nucleon group transfer mechanism in a surface interaction followed by de-excitation via nucleon emission from the excited intermediate. Thus the energy dependence of recoils and cross sections of single nucleon and multinucleon transfer products have been calculated and found in good agreement with experimental results.     

Yield of fission fragments from the photofission of actinide nuclei

Yields of the ¹⁰¹Mo, ¹³⁵I, and ^135m Cs isotopes from the photofission of the actinide nuclei ²³²Th ²³⁸U, and ²³⁷Np are measured. These fission fragments have specific nuclear structure features or are of practical use. The measurements are performed in the bremsstrahlung from the microtron of the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research (JINR) at an electron energy of 22 MeV. The yields of the fragments are measured by the activation method using a γ radiation HPGe detector.     

Low-temperature electrolytic coloration and spectral property of ammonium alum crystals

Ammonium alum crystals are colored electrolytically using a pointed cathode and a flat anode at low temperatures and under various voltages. SO₃^?, SO₂^? and O₃^? hole-trapped centers are produced in colored ammonium alum crystals. Characteristic absorption bands of SO₃^?, SO₂^? and O₃^? hole-trapped centers are observed in absorption spectra of colored ammonium alum crystals. Production and conversion of hole-trapped centers are explained. Current–time curves for electrolytic coloration of ammonium alum crystal and their relationship with electrolytic coloration process are given.     

Excited states of 176Hf

The properties of the excited levels of the even-even deformed nucleus ¹⁷⁶Hf are analyzed on the basis of available experimental data on ¹⁷⁶Ta decay. Thirty-nine new states are included in the energy-level scheme of the ¹⁷⁶Hf nucleus. The deexcitation of a number of known levels is supplemented with new transitions. New levels are included in three rotational bands, and the K _i =0 ₄ ⁺ band is identified. The 2470.95-keV level is considered as a two-phonon quadrupole-octupole state. A strong interplay of states belonging to different bands is indicated. The Coriolis interaction is calculated for pairs of K ^π = 0^? and 1^?, 0⁺ and 2⁺, and 2⁺ and 3⁺ bands. The interaction parameters are found. It is shown that the sets of positive-and negative-parity states are connected by El transitions characterized by large hindrance factors.     

High-resolution Fourier spectra of carbon dioxide and three of its isotopic species near 4.3 μm

Low-pressure, Doppler-limited absorption spectra of ¹⁶O¹²C¹⁶O, ¹⁶O¹³C¹⁶O, ¹⁶O¹²C¹⁷O, ¹⁶O¹²C¹⁸O have been recorded in the 4.3-μm region with a high-information Fourier transform interferometer operating in a vacuum. About 700 absolute wavenumbers achieving at least a tenfold improvement in accuracy over previous measurements are reported with an accuracy of the order of 0.12 × 10^?3 cm^?1 (or 3.5 MHz). They may consequently be used as secondary standards. More than 70 molecular constants are reported in this paper.     

Self-consistent field description of high spin states in rare earth nuclei

The Hartree-Fock-Begoliubov cranking equations are solved for ^{168, 170}Yb and ¹⁷⁴Hf. Deformation and pairing properties are both obtained with a G-matrix derived from the Reid soft-core potential. The high spin anomalies are attributed to the disappearance of the neutron pair gap in ¹⁶⁸Yb, the realignment of an $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$. neutron pair in ¹⁷⁰Yb, and a combination of these two mechanisms in ¹⁷⁴Hf. Two bands intersecting at high spin are found for ¹⁷⁴Hf.     

A simple classification of resonant heavy-ion collisions

Simple diagrams based on the relative location of the effective barriers of direct channels are shown to select known resonant heavy-ion collisions. Other systems are predicted to exhibit a resonant behaviour, mainly ¹⁶O + ³²S, ²⁸Si + ³²S and ²⁸Si + ⁴⁰Ca.     

Analysis of parity-violating asymmetries in elastic electron-nucleus scattering

Parity violating asymmetries in elastic electron scattering on nuclei with arbitrary spin and isospin are considered in detail, extending our previous work on this matter [1]. Examples are given for the target nuclei¹²C,⁴⁰Ca,²⁰⁸Pb,³H,³He,⁴¹Ca,²⁰⁹Bi. Several ways of extracting information on the structure of weak neutral current couplings are presented. Besides, as a further possibility to check the validity of the standard gauge model [2] at intermediate energies, the chances to distinguish among different classes of gauge models are discussed.     

The Inverse Problem of Argon Diffusion from Minerals: Determination of Kinetic Parameters from Stepwise-Heating Experiments

Abstract

Results of two routine ⁴⁰Ar/³⁹Ar stepwise heating experiments on a biotite and a basanite are interpreted in terms of Fick's and Arrhenius' laws. Both patterns represent a saddle-shaped ³⁹Ar release. Argon isotope spectra are suggested to be controlled by the activation energy of diffusion E and the frequency factor D_o . The activation energy of ³⁹Ar is lower than the one of ⁴⁰Ar. This results in a preferable release of ⁴⁰Ar relatively to ³⁹Ar at high-temperature steps and an increasing high-temperature wing in the saddle-shaped age spectrum. At low temperatures, considerable losses and irregularities in release of mainly ³⁹Ar are observed, which cause the decreasing low-temperature wing in the “saddle”. The suggestion of argon losses (mainly of ³⁹Ar) from a loose, “unstable” zone of the mineral structures becomes justified. The n-irradiation of the samples and the shift of E of ³⁹Ar towards lower values seems to explain the saddle-shaped age-spectra often encountered in ⁴⁰Ar/³⁹Ar-geochronometry.